Libraries: Use default constructors/destructors in LibJS

https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#cother-other-default-operation-rules

"The compiler is more likely to get the default semantics right and
you cannot implement these functions better than the compiler."

Userland/Libraries/LibJS/Interpreter.h

@@ -101,7 +101,7 @@ public:
 
     static NonnullOwnPtr<Interpreter> create_with_existing_realm(Realm&);
 
-    ~Interpreter();
+    ~Interpreter() = default;
 
     ThrowCompletionOr<Value> run(Script&);
     ThrowCompletionOr<Value> run(SourceTextModule&);